The Liquid Method Ultrafine And Nano Co. <sub> 3 </ Sub> O <sub> 4 </ Sub> Powders And Characterization

Ultrafine, nano-Co3O4 powder has extensive applications in the fields of catalyst, super capacitors and ceramic materials. Especially in recent years as China's electronics industry and communications industry flourish, the demand of the lithiμm ion secondary battery has been growing explosively. As a raw material of lithium-ion battery electrode, Co3O4 powder is also in growing demand. However, with those internationally well-known manufacturers, the current quality level of domestical-made Co3O4 powder is relatively low, which hampers the development of Chinese lithiμm-ion rechargeable battery industry. The purpose of this study is to explore the manufacturing techniques that are suitable for industrial production of high-quality Co3O4 Powder.Two methods were approached to prepare Co3O4 powder in this study, namely, high-pressure hydrothermal method and ammoniμm bicarbonate precipitation-thermal decomposition method. In high-pressure hydrothermal method Co(Ac)2·4H2O and Co(OH)2 were used respectively as starting materials. The effects of reaction temperatures, reaction time and concentration of Co(Ac)2·4H2O on the final yields,BET specific surface area and calculated BET particle size were investigated. By ammoniμm bicarbonate precipitation-thermal decomposition method, cobalt precipitate was prepared using NH4HCO3 and CoCl2·6H2O as starting materials. Co3O4 powder was obtained after thermal decomposition of cobalt precipitate. This study investigated the effects of Co2+ concentration, reaction temperature, surfactant, content of Cl- in precursor and the process of thermal decomposition on the morphology, particle size and phase composition of Co3O4 powder.The main conclusions illustrated are follows:1. Spherical Co3O4 nanoparticles are prepared by high-pressure hydrothermal method using Co(Ac)2·4H2O as starting material. As the reaction temperature elevates, the yield of cobalt increases and the average grain size of Co3O4 increases; As the reaction time extends, the yield of cobalt increases and the average powder grain size increases. As the concentration of Co(Ac)2·4H2O increases, the yield of cobalt is increasing slowly. But when mol concentration of Co(Ac)2·4H2O is 0.5 mol/L, the particle size reaches the minimμm value, but if the solution concentration increases more, the average particle size enlarges.2. Spherical Co3O4 Ultrafine particles with high purity are prepared by high-pressure hydrothermal method using Co(OH)2 as starting material. Compared with the method of Co(Ac)2·4H2O, the particle size of the powder is large, while the size of the crystallite is small.3. It is found in the research of preparing the ultra-fine powder CO3O4 by ammoniμm bicarbonate precipitation-thermal decomposition method that as the concentration of cobalt solution increases, Co3O4 particle size decreases, and the particles become more conglomerated; as the reaction temperature elevates, Co3O4 particle size increases; If the surfactant CATB is added the powder's conglomeration will be reduced, which simultaneously causes the particle size to reduce.4. In the thermal decomposition process, the Co3O4 powder's morphology has a certain succession to the forerunner body powder's morphology; When the thermal decomposition temperature is 400℃or 850℃, the powder has CoO phase component, when the temperature is 600℃, the product consists of single Co3O4 phase with cubic spinel structure.5. The content of chlorine in precursor has a great effect on the morphology of Co3O4 powder prepared by thermal decomposition method. Single-crystal Co3O4 powder with crystalline perfection can be prepared by controlling the content of chlorine in precursor.